Bell ringing circuit and switch therefor



Oct. 29, 1935. s. T. FARRELL 2,019,075

BELL RINGING CIRCUIT AND SWITCH THEREFOR Original Filed April 7, 1932 Fly. 1

I A 1\ /a a a P15. .2 a H INVENTOR iiATTORNEY.

Patented Oct. 29, 1935 PATENT OFFICE BELL RINGING CIRCUIT AND SWITCH THEREFOR Bartholomew T. Farrell, Manchester, N. H.

Application April 7, 1932, Serial No. 603,773 Renewed March 22, 1935 1 Claim.

This invention relates to electric bell circuits and to switches for controlling such circuits.

It has been the usual practice heretofore to depend upon batteries as the source of supply 5 of current for operating door bells and bells used generally for call purposes, alarms, and the like.

At the present time it is becoming fairly common, however, to replace such batteries with a small step down transformer which is constantly connected with the alternating current supply circuit, the bell or bells being controlled by simple push button switches located in the secondary circuit of the transformer.

In such an arrangement the transformer constantly takes enough current to supply its copper and core losses. Transformers, such as those now used for this purpose, consume in the neighborhood of three watts continuously, even when the bell circuit is open. In addition to this loss, an installation of the character above described also involves a substantial fire hazard because of the liability of the transformer to burn out due to the constant load imposed on it and to the gradual deterioration which necessarily occurs in such apparatus. This fact has been recognized and special regulations have been issued in some localities concerning the installation of transformers used for this purpose.

The present invention deals with these circumstances. It aims to improve systems of this type with a view to minimizing the losses and the fire hazard above described.

The nature of the invention will be readily understood from the following description when read in connection with the accompanying drawing, and the novel features will be particularly pointed out in the appended claim.

In the drawing,

Figure 1 is a plan view of a switch embodying features of this invention;

Fig. 2 is a vertical, sectional view on the line 2-2, Fig. 1; and

Fig. 3 is a diagrammatic view of a bell ringing circuit arranged in accordance with this invention.

Referring first to Fig. 3, the system there shown comprises a small transformer 2 which may be of the type commonly used for bell ringing purposes. The primary coil of this transformer is connected through suitable conductors and through a fuse block 3 with the alternating current house lighting circuit wires 4. Similarly, the secondary coil is connected through suitable conductors with an electric bell 5. The flow of current through both of these circuits is controlled by a single switch. In the particular arrangement shown two stationary contacts 6 are connected in the primary circuit, while two ad-' ditional contacts 1 are connected into the secondary or bell circuit. A movable contact 8 5 carried by a plunger I0 is arranged to electrically connect the two contacts 6, while a similar contact 9, also carried by the pltmger I0, is arranged to engage both of the stationary contacts l. 10

Normally both switches are held open by means of a spring, and so long as the parts remain in this condition no current can flow through either the primary or secondary circuit. When it is desired to ring the bell 5 the push button 12 on 15 the end of the plunger I0 is forced inwardly, thus closing both switches substantially simultaneously, whereupon the bell will ring so long as the switches remain closed. As soon as the pressure on the push button is relieved the spring will 20 return it to its original position and open both the primary and secondary circuits.

Additional bells may be operated from the transformer 2 by suitable connections in parallel with those above described, and such an arrangement is illustrated in Fig. 3, the parts corresponding to those above described being indicated by similar but primed numerals.

It will be evident that with this arrangement the transformer takes current only when the bell 30 is ringing. At all other times the primary circuit is open and no energy, therefore, is being consumed anywhere in the bell system. This not only avoids the waste of power which has been a necessary incident to the use of prior systems of this character, but it also eliminates the fire hazard which has attended the use of these transformers in earlier systems.

A switch structure especially adapted for use in this system is illustrated in Figs. 1 and 2. It is essentially like that shown diagrammatically in Fig. 3 and the corresponding parts are indicated by the same numerals used for them in said figure. The contacts are enclosed in a casing [4 which may conveniently be made of vulcanite, bakelite, or any other suitable insulating material that can be molded. Preferably the main body of the casing is provided with a transverse partition l5 which divides the space in the casing into upper and lower chambers, the contacts 50 6 being mounted in the lower chamber, while the secondary contacts I are located in the upper chamber. This arrangement is of advantage in maintaining the conductors and contacts carrying the potential 01' the lighting circuit well separated from those which carry only a very low voltage. Preferably theprimary circuit wires will be led to the switch in a suitable protective casing or covering, and the lower end of the switch,

The spring which normally holds the push button l2 in its projected position is shown in Fig. 2 at l8. It abuts at one 'end against the lower surface of the push button and at its opposite end against the partition IS.

The switch casing includes a cover plate 20 through which the end 01' the push button l2 normally projects, this cover and the flange of the body portion [4 oi. the casing having registering holes 2l-2l to receive screws for holding the entire'casing in place. The switch casing can also be used to support a name plate, the name being printed or engraved on a disk which is clamped between the cover 20 and the flange of the casing body I4. A curved aperture 22 is formed through the cover plate to expose the name on the disk.

While I have herein shown and described a preferred embodiment of my invention, it will be evident that some featuresv of the invention are susceptible of embodiment in other forms without departing from the spirit or scope thereof.

Having thus described my invention, what I desire to claim as new is:

A bell ringing system wherein current passes through the transformer only when the switches are closed, comprising a transformer including primary and secondary coils, a plurality of bells, a circuit for each bell connected to the secondary of the transformer, switching means for each bell circuit adapted to close the primary circuit and the secondary circuit for each bell respectively, and means for biasing said switches to open circuit position.

BARTHOLOMEW T. FARRELL. 

